go/internal/srcimporter: simplify and fix package file lookup

The old code was a blend of (copied) code that existed before go/build,
and incorrect adjustments made when go/build was introduced. This change
leaves package path determination entirely to go/build and in the process
fixes issues with relative import paths.

Fixes #23092
Fixes #24392

Change-Id: I9e900538b365398751bace56964495c5440ac4ae
Reviewed-on: https://go-review.googlesource.com/83415
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/go/internal/srcimporter/srcimporter.go

@@ -46,9 +46,9 @@ func New(ctxt *build.Context, fset *token.FileSet, packages map[string]*types.Pa
 // for a package that is in the process of being imported.
 var importing types.Package
 
-// Import(path) is a shortcut for ImportFrom(path, "", 0).
+// Import(path) is a shortcut for ImportFrom(path, ".", 0).
 func (p *Importer) Import(path string) (*types.Package, error) {
-	return p.ImportFrom(path, "", 0)
+	return p.ImportFrom(path, ".", 0) // use "." rather than "" (see issue #24441)
 }
 
 // ImportFrom imports the package with the given import path resolved from the given srcDir,
@@ -62,23 +62,10 @@ func (p *Importer) ImportFrom(path, srcDir string, mode types.ImportMode) (*type
 		panic("non-zero import mode")
 	}
 
-	// determine package path (do vendor resolution)
-	var bp *build.Package
-	var err error
-	switch {
-	default:
-		if abs, err := p.absPath(srcDir); err == nil { // see issue #14282
-			srcDir = abs
-		}
-		bp, err = p.ctxt.Import(path, srcDir, build.FindOnly)
-
-	case build.IsLocalImport(path):
-		// "./x" -> "srcDir/x"
-		bp, err = p.ctxt.ImportDir(filepath.Join(srcDir, path), build.FindOnly)
-
-	case p.isAbsPath(path):
-		return nil, fmt.Errorf("invalid absolute import path %q", path)
+	if abs, err := p.absPath(srcDir); err == nil { // see issue #14282
+		srcDir = abs
 	}
+	bp, err := p.ctxt.Import(path, srcDir, 0)
 	if err != nil {
 		return nil, err // err may be *build.NoGoError - return as is
 	}
@@ -115,11 +102,6 @@ func (p *Importer) ImportFrom(path, srcDir string, mode types.ImportMode) (*type
 		}
 	}()
 
-	// collect package files
-	bp, err = p.ctxt.ImportDir(bp.Dir, 0)
-	if err != nil {
-		return nil, err // err may be *build.NoGoError - return as is
-	}
 	var filenames []string
 	filenames = append(filenames, bp.GoFiles...)
 	filenames = append(filenames, bp.CgoFiles...)

src/go/internal/srcimporter/srcimporter_test.go

@@ -10,6 +10,7 @@ import (
 	"go/types"
 	"internal/testenv"
 	"io/ioutil"
+	"path"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -200,3 +201,34 @@ func TestIssue20855(t *testing.T) {
 		t.Error("got no package despite no hard errors")
 	}
 }
+
+func testImportPath(t *testing.T, pkgPath string) {
+	if !testenv.HasSrc() {
+		t.Skip("no source code available")
+	}
+
+	pkgName := path.Base(pkgPath)
+
+	pkg, err := importer.Import(pkgPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if pkg.Name() != pkgName {
+		t.Errorf("got %q; want %q", pkg.Name(), pkgName)
+	}
+
+	if pkg.Path() != pkgPath {
+		t.Errorf("got %q; want %q", pkg.Path(), pkgPath)
+	}
+}
+
+// TestIssue23092 tests relative imports.
+func TestIssue23092(t *testing.T) {
+	testImportPath(t, "./testdata/issue23092")
+}
+
+// TestIssue24392 tests imports against a path containing 'testdata'.
+func TestIssue24392(t *testing.T) {
+	testImportPath(t, "go/internal/srcimporter/testdata/issue24392")
+}

src/go/internal/srcimporter/testdata/issue23092/issue23092.go

@@ -0,0 +1,5 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue23092

src/go/internal/srcimporter/testdata/issue24392/issue24392.go

@@ -0,0 +1,5 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue24392